watchdog is a daemon that periodically pokes a hardware chip,
 and if it fails to do so (presumaby because the system got stuck),
 the chip would reboot the system. A somehow working software
 emulation of this chip, called "softdog" also exists in Linux.
 A reboot can be triggered by some other criteria too.

This script installs a RedHat-style initscript, but you can run it from
/etc/rc.d/rc.local too.

This daemon needs a proper kernel driver to work.
Some machines, such as raspberry pi 4b, provide /dev/wachdog by default.
Intel systems might require editing /etc/sysconfig/watchdog to have
START_MOD_CMD="modprobe iTCO_wdt" and

You can try "softdog" if nothing better is available.
